Electric plug receptacle



March 11, 1958 A. E. PIPLACK 2,826,652

ELECTRIC PLUG RECEPTACLE Filed April 24, 1956.

I ARNo E. PIPLACK United States Patent ...is impossible for .a child to receive a shockcby inserting .ametal object into it.

.Another object is the provision-of a receptacle having a contact arrangement which ensures a-very firms-and positive contact-with the prongs of a plug whichhave been inserted into it.

.Another objectv is the provision of a safety electrical receptacle of. comparatively simple :and inexpensive con- .struction.

The electricgplug receptacles now in common use include apair of slots for receiving the-prongs of an electric plug, these prongs engaging contactskinzthe receptacle in line with theslots thereof to make the xlesired electrieconnection. A large percentage of these receptacles are used in homes-where they'are usuallylocated neanthe floor. This means that a young child canin- .sert.small fiat articles into the slots,-a.ud iii a childdoes tthis-witha metal article,.he receives an electric shock. As is well known, this is very.dangerous.

With :the .present invention, .a child may ..insert :a

r-metal object, suchnas' a-. fingernail file,.into a slot of-the .receptacle withno .chance of'receiving a shock. In vfact,.eveni-ithe' were to insert metal objects .in -:both

slots he would not normally receive a shock.

A plug. receptacle according to; the present invention includes a bodyhaving a pairof spaced parallel slots extending therethrough,'a control arm mounted :near

the inner end of each slot and normally extending yangularly across said'slot end, a contact movably. mounted-on-the body near each slot co-operating with-and 40 spaced from the arm near the other sl0t,='non-conducting means connecting each movable contact .with its .zco-

operating arm for movement therewith, and a fixed contact near and normallyspaced from each movable contact. When the prongs of an electric plug are :in- ,-serted in and moved through the slots,vthey engage the control arms and move them to shift the :movable contacts into engagement with the fixed contacts.

-An exampleof this invention. is illustrated inzthe'accompanying drawings, in which,

Figure .l is a plan view of a pair of receptacles mount- .ed ;.in. a receptacle box,

Figure 2 is an-enlarged-cross sectionttakenon the line :2-2-of Figure 1, without theelectric 'plu'g in:the

. receptacle,

Figure -3 is a view.simi1ar to Figure 2 showing -a plug with-its prongs in the receptacle,

Figure 4 is a longitudinal sectional view taken on the line 4-4 of Figure l,

Figure:5 is. a perspective view of the control arm and ...movable contact assembly shown in Figures 1 to 4, :and

figure/.6 is a perspective view of an alternativeformof .control arm and movable contact assembly whichmay "ice 2 normally is round, ::as;=shown. :In this duplex receptacle there: are twonfithese bodies arranged side by side and connected r-byrsa web 11. The body is formed of a .suitable non'-conducting;material, such as a hard plastic. 5 =The bodyf.l;0thaszouter and inner ends 12 and 13,-and

alpair of.spacednslots-sl5:.and:16 extending throughthe body from the outer towards the inner endvthereof, as clearly 'shownminiEigures-l and .3. These slots are long enonghlzandcspaced" the right "distanceapart to re- -ceiver thesprongsclis andilQ-ofa standard electrical plug 'lnttheiillustnated form of .the: invention, 1 azcomparatively 'ilarge recess 23'::is .formed1in;'.the inner end ofi the plug body and: opens outwardly therefrom.

teams-charms 25 zanidzzfii are mounted. on. thexb'odys near 15 zthe'rinnerzends :cfzthezslots 15 and 16,. respectively,: and nomnallyt extcndsangularly across .the adjacent ends :of theiraslots. Movableccontactsilitl and .31 are mounted sonithe bo'dy near slots lsand 16 tow-operate with arms-26 andl25i'respectively. iFor. simplicity and ease of-"manufacture arm 25' and contact :30 may be formed :from ar single-piece of-springy' metal bent into. a substantialty v :shape, the :apex' 33: or the" vi extending around. a

the body 10. A= potti0r1 350i the body acts ---as astop for contact 30. Similarly, arm 26 andcontact 25 "SI-are for-med from; a'singlea piece of springly metal bent intoa M ttie: apex 5$zof which extends around apin-39 in-the plu ibodyc ="A portion40of saidbody acts-. as a -:stop for arm 31.

Suitable 'non-conductingmean's' connect the movable 30 contacts 30 and" 31 in any =suita'ble manner' with their co-operating arms 26 and 25 for movement therewith; one

-:way ofixloing this" being illustrated: in r the I drawings. A

"portion 43 of the metal forming: contact-30 'isbent back 'on itselfi 'and: has a tug-44 projecting inwa'rdly' therefrom 5 in. line..with' the outer end at control--arm 2'6,- said arm end also having a lug 45 thereon. 'A connector "47 formed oftsuita'ble inshlating'm'aterial extends between andis 'connec'ted at its endsto the aligned-lugs and 45. Similarly, the portion-=48 of the metal' forming movable contact .31 is bent back on itself, and has-a lug 50=- projecting inwardly therefrom in-line with another lug-51 on'the innerend of control 'arm '25. An insulating connector .-53.extends between and is-secured at=itsend to aligned lugs- 50 and 51.

Pixedscontacts-58 '-and 59 aremounted near and normally spaced from the movable contacts 30 and 31, respectively. Irrthis example, the fixedcontacts are mount- .edonxa suit'able 'base 62 formed'of insulating material spaced a little from-body 10. If desired, the base'may be'zconnected to the plug 'body bystraps -65-an*d 66, preferably formedof insulating material. Contacts 58 and :59 are secured to base-62 and extend towards movable contacts 30 and 31, but the inner ends of the fixed contacts are normally 'space'd'from the adjacent ends of the movable .contacts.

With-a duplex receptacle, contacts 58-and 59 may be made long-enough to-serve-both receptacles, as clearly shown; in; Figure -'4.

The illustrated duplex receptacle is shown mounted in a receptacle box 0 indthe customary manner. Connectors Wand-'73 extendoutwardlyfrom the plug' bodies Nandsaresecurdd to 'portionsof the box" by screws 74 :and 75. 'Whemthezdevie'e is inuse, wires 78 and' 79, see Figures 2qand. 3,:extend.:into theb'ox. and are connected to contacts 58E and- 591i terminals 80' and 81.

Normal ly movable contacts :30 and'31 are spacedfrom fixed: contacts 58.-and: 59, asshown in;Figure 2. When the prongstls and .19 of plugs 20 are inserted in slots 15 and.16,.they engage control arms 25 and 26'and cause them-.to-swing about pins34 and 39. Movement ofarm 25 draws contact.31. into engagement with contact 59. At the same time, movement of arm 26 draw stop 35. At the same time, the metal forming contact 31 bends around pin 39. The same thing happens to arm 26 and contact 30. Therefore, it takes a reasonable amount of pressure to swing the control arms outwardly away from each other and the movable contacts towards each other.

If the child inserts a metal object in one of the receptacle slots, it will touch the control arm extending across the slot, but this will not result in a shock to the child possible for a child to be injured by an electrical shock.

The control arm and movable contact assembly of Figures l to 4 is clearly shown in Figure 5. It will be noted that a large notch 82 is formed in arm 25, lug 51 and connector; 53 in order to permit the portion of the adcontact therewith. .Similarly, lug 45 is formed with .a

.large notch 84'to permit a'portion of arm to pass through without coming into contact with them. If dejacentconnector 47 and lug 45 to pass the arm without 1 sired, a portion 86 of insulating connector 47 may be folded lover the notched edge of lug 45 to be sure that said lug doesnot touch arm 25 or lug 51.

Figure 6'illustrates an alternative form of control arm and movable contact assembly which may be used in place of the one shown in Figure 5. In this alternative, I

a control arm 25a and movable contact 30a are formed from a single V-shaped piece of springy metal, while control arm 26a and ,movable contact 31a are formed from another V-shape'd piece of springy metal. When installed in the plug body 10, arm and contact 25a--30a fit around pin 34, and arm and contact 26a-31a fit around pin 39. A non-conducting connector 88 extends between arm 25a and contact 31a and is connected thereto in any convenient manner. This may be done by inserting the bent ends 89 and 90 of the connector under pressedout portions 91 and 92 in the arm and contact, respectively. Another non-conducting connector 95 extends between arm 26a and contact 30a and is connected at its opposite ends thereto in the same manner as connector 88 is connected to its arm and contact. A notch 98 may be formed in arm 26a in order to permit connector 88 to pass thereby without contact therewith.

The assembly of Figure 6 functions in the same manner as that of Figure 5.

What I claim as my invention is:

1. In an electric plug receptacle, a body having outer and inner ends, a pair of spaced parallel slots extending through the body from the outer towards the inner end thereof, a conductor control arm mounted on the body near the inner end of each slot and normally extending angularly across said slot end, a contact movably mounted on the body near each slot electrically connected to the arm near said slot and co-operating with and spaced from the arm near the other slot, non-conducting means connecting each movable contact with its co-operating arm for movement therewith, and a fixed contact near and normally spaced from each movable contact, whereby when the prongs of an electric plug are inserted'in and moved through the slots they engage the control arms and move them to shift the movable contacts respectively connected thereto into engagement with the fixed adjacent contacts so that each prong and the control arm touching 4 it with the movable contact electrically connected thereto and the fixed contact engaging the latter form an electrical current path created by the movement of the other control arm.

2. An electric plug receptacle as claimed in claim 1 in which the control arm of each slot and the movable contact near said slot are formed of a single V-shaped piece of springy metal, the free end of said arm being connected to the movable contact of the other slot bythenonconducting means. Y

3. An electric plug receptacle as claimed in claim 2 in which the apex of each V-shaped piece of metal extends around a pin carried by the receptacle body.

4. In an electric plug receptacle, a body formed of non-conducting material having outer and inner ends, a pair of spaced parallel slots extending through the body from the outer towards the inner end thereof, a conductor control arm mounted on the body near the inner end of each slot and normally extending angularly across said slot end, a contact movably mounted on the body near each slot electrically connected to the arm near said slot and co-operating with and spaced from thejamr near the other slot, said arms'extending across their respective slots towards each'other and the movable con tacts extending away from each other, non-conducting means connecting each movable/contact with its co-operating arm for movement therewith,'-and a fixed contact near and normally. spaced from each movable contact, whereby when theprongs of an electric plug are inserted in and moved through the slots they engage the control spectively connected --thereto into engagement with the :fixed adjacent-contacts so that each prong and thecontrol arm touching :itwith the movable contact electrically connected thereto and the fixed contact engaging the latter form'an electrical current path of the other control arm. r

5. An electric plug receptacle as claimed in claim 4 in which the non-conducting means are connectors extending from the ends of their control arms to their movable con tacts, said connectors being substantially parallel.

6. In an electric plug receptacle, a body formed of non-conducting material having outer and inner ends,- a large recess in the inner endof the body opening-outwardly therefrom, a pair of spaced parallel'slots extending through the body from the outer end to the recess, a conductor control arm mounted on the body in the createdby the movement 1 recess thereof near the inner end of each slot and normally extending angularly across said slot end, a contact movably mounted on the body in the recess near each slot electrically connected to the arm near said slot and cooperating with and spaced from the arm near the other slot, said arms extending across their respective slots towards each other and the movable'contacts extending away from each other, non-conducting means connecting each movable contact with its co-operating arm for movement therewith, and a 'fixed contact near and normally spaced from each movable contact, whereby when the prongs of an electric plug are inserted in and moved through the slots they engage the control arms and move them to shift the movable contacts respectively connected thereto into engagement with the fixed adjacent contacts so that each prong and the control arm touching it with the movable contact electrically connected thereto and the fixed contact engaging the latter form an electrical current path created by the movement of the other control arm.

'References Cited in the file of this patent UNITED STATES PATENTS 2,500,474 Sperrazza Mar. 14,1950 2,531,625. Hubbell Nov. 28, 1950 2,540,496 Sperrazza Feb. 6, 

